Perfumed products are well-known in the art. However, consumer acceptance of such perfumed products like laundry and cleaning products is determined not only by the performance achieved with these products but also by the aesthetics associated therewith. The perfume components are therefore an important aspect of the successful formulation of such commercial products.
In addition, a clay mineral compound is a desirable ingredient of such laundry and cleaning product, in particular those products which are in tablet form.
Indeed, the clay can provide softening benefit but can also serve as a disintegrant of such detergent tablets.
However, a problem encountered with perfumed detergent tablets containing a clay mineral compound is that the clay can have a detrimental effect on the performance of the perfume contained therein. Hence, not to be bound by theory, it is believed that due to the close physical proximity given by the tablet, the perfume is absorbed into the clay where it can interact with heavy metal ions and acid or base sites within the clay which as result may cause a discoloration of the clay. Still, the interaction between the perfume and the clay may also result in the tablet having a less attractive odour.
Accordingly, it is an object of the invention to provide a perfumed detergent tablet comprising a clay mineral compound which exhibit good perfume performance with reduced discoloration of the clay.
Further, cleaning compositions in tablet form have often been proposed, however these have not (with the exception of soap bars for personal washing) gained any substantial success, despite the several advantages of products in a unit dispensing form. One of the reasons for this may be that detergent tablets require a relatively complex manufacturing process. In particular, it is often desirable to provide the tablet with a coating and this adds to the difficulties of manufacture.
While tablets without a coating are entirely effective in use, they usually lack the necessary surface hardness to withstand the abrasion that is a part of normal manufacture, packaging and handling. The result is that non-coated tablets suffer from abrasion during these processes, resulting in chipped tablets and loss of active material.
Finally, coating of tablets is often desired for aesthetic reasons, to improve the outer appearance of the tablet or to achieve some particular aesthetic effect.
Numerous methods of tablet coating have been proposed, and many of these have been suggested for detergent tablets. However, all of these methods have certain disadvantages, as will be explained below.
GB-A-0 989 683, published on 22nd Apr. 1965, discloses a process for preparing a particulate detergent from surfactants and inorganic salts; spraying on water-soluble silicate; and pressing the detergent particles into a solid form-retaining tablet. Finally, a readily water-soluble organic film-forming polymer (for example, polyvinyl alcohol) provides a coating to make the detergent tablet resistant to abrasion and accidental breakage.
EP-A-0 002 293, published on 13th Jun. 1979, discloses a tablet coating comprising hydrated salt such as acetate, metaborate, orthophosphate, tartrate, and sulphate.
EP-A-0 716 144, published on 12th Jun. 1996, also discloses laundry detergent tablets with water-soluble coatings which may be organic polymers including acrylic/maleic co-polymer, polyethylene glycol, PVPVA, and sugar.
WO9518215, published on 6th Jul. 1995, provides water-insoluble coatings for solid cast tablets. The tablets are provided with hydrophobic coatings including wax, fatty acid, fatty acid amides, and polyethylene glycol.
EP-A-0 846 754, published on the 10th of Jun. 1998, provides a tablet having a coating comprising a dicarboxylic acid, the coating material typically having a melting point of from 40° C. to 200° C.
EP-A-0 846 755, published on the 10th of Jun. 1998, provides a tablet having a coating comprising a material insoluble in water at 25° C., such as C12–C22 fatty acids, adipic acid or C8–C13 dicarboxylic acids.
EP-A-0 846 756, published on the 10th of Jun. 1998, provides a tablet having a coating comprising a disintegrant material and preferably an effervescent material.
Recently, it has been found means by which coated tablets can be provided with a coating so that they can be stored, shipped and handled without damage, the coating being easily broken when the tablet is in the washing machine, releasing the active ingredients into the wash solution. Typical of such disclosure can be found in pending European patent applications EP 99870017.3, publication date Aug. 9, 2000, EP 99870018.1, publication date Aug. 9, 2000, and EP 99870019.9, publication date Aug. 9, 2000.
However, whilst giving satisfactory results, it has now also been found that where a clay mineral compound is present in the coating of the detergent tablet, the clay, for the same believed reasons stated above, can have a detrimental effect on the performance of the perfume contained therein as well as on the appearance of the coating, i.e. discoloration of the coating.
These problems have further been found more acute overtime, and more particularly where the coating also comprises an acid having a melting point of at least 40° C., more particularly with a melting point of at least 145° C.
Accordingly, the detergent formulator is also faced with the problems of providing a coated tablet having a coating which has satisfactory appearance, is sufficiently hard to protect the tablet from mechanical forces when stored, shipped and handled, and disperses readily in an aqueous solution whilst still giving satisfactory perfume performance.
Further, the perfuming of detergent tablet is a concern to the detergent formulator. Hence, the presence of the coating on the tablet can reduce the diffusion of the perfume from the tablet resulting in a less attractive odour.
It has now surprisingly been found that the addition of a heavy metal ion sequestrant to perfumed detergent tablet overcomes these problems.